1. Field of the Disclosure
This invention relates generally to dual position media registration and media pre-transfer baffle geometry, and more particularly, to a two-position pre-transfer apparatus that enables printing onto heavy weight media.
2. Description of Related Art
In a typical electrophotographic printing process, a photoconductive member is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charges thereon in the irradiated areas. An electrostatic latent image is thus recorded onto the photoconductive member corresponding to the informational areas contained within the original document. After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner powder image is then transferred from the photoconductive member to a copy sheet, for example, as shown in U.S. Pat. No. 5,761,596 to William G. Osbourne et al. The toner particles are heated to permanently affix the powder image to the copy sheet.
However, existing media pre-transfer geometry limits the pre-processing of heavy media weights based on its inherent “S” baffle pre-transfer geometry as shown in prior art FIG. 1. The packaging industry, in most cases, requires greater than 350 gsm media to be images. This media weight requirement creates a limitation with the pre-transfer and registration hardware of current machines such as shown in FIG. 1.
For example, in Prior Art FIG. 1, the pre-transfer baffle gap between baffles 16 and 17 allow for an “S” shaped buckle to form in the media 18 with an angle of engagement of media 18 with photoreceptor 10 of about 28°. This allows for some mismatch in velocities of a registration nip formed between idler roll 14 and drive roll 15 and the photoreceptor 10 which is entrained around drive roll 11 and idler roll 12. An idler roll 13 is used to maintain frictional contact between sheet 18 and photoreceptor 10. A larger transfer baffle gap allows for the formation of buckles and can lead to lead edge stubbing with curled sheets. Both characteristics degrade registration and transfer performance on heavy weight media.
Hence, wider media weight latitude, allowing printers to migrate into the packaging and other industries is required.